Proline-rich proteins (PRPs) make up about seventy percent of the salivary proteins. See Kim, et al., the structure and evolution of the human salivary proline-rich protein gene family, Mammalian Genome, 4: 3-14 (1993); Bennick A., Salivary proline-rich proteins. Molecular and Cellular Biochemistry 45: 83-99 (1982). The PRPs are divided into three groups (acidic, basic, and glycosylated) on the basis of their electrophoretic and chemical properties. Biological activities of PRPs include binding hydroxyapatite, calcium, and certain intraoral bacteria; mediation of adherence of microorganisms to the tooth surface; inhibition of hydroxyapatite formation; modification of lubricative properties of saliva; and detoxification of dietary tannins.
Six PRP genes code for many of the salivary PRPs. These PRPs show frequent polymorphisms. Azen, E. A., et al. Am. J. of Human Genetics, 58:143 (1996). Single PRP genes produce multiple PRPs by allelic variation, post-translational cleavage, and differential mRNA processing. Maeda, N., et al. J. of Biol. Chem., 260:11123 (1985).
CON-1, a member of the PRP gene family, is a basic glycoprotein which binds concanavalin A. Approximately, 80 percent of the population has a form of CON-1, referred to as the large form, 10 percent the small form (CON-2), and 10 percent are missing CON-1 altogether. The CON-1 protein has proven extremely difficult to purify and characterize because of its rapid degradation in saliva.
It has been found that CON-1 and its analog, CON-2, are highly potent alpha-glucosidase inhibitors. Such inhibitors of synthetic origin have shown efficacy in treating certain medical conditions.
Alpha-glucosidases are enzymes which hydrolyze both alpha-1,4 and alpha-1,6 glycosidic linkages. Cleaving d-1,4- and d-1,6-linkages result in the conversion of non-absorbable carbohydrates into absorbable sugars during the digestion of foods. The proper post-translational processing of glycoproteins also requires cleavage of part of the oligosaccharides. Synthetic inhibitors of alpha-glucosidase have proven useful in the treatment of diabetes and show potential for the treatment of retroviral infections such as those caused by HIV.
Acarbose is an alpha-glucosidase inhibitor widely used to treat diabetic patients. Acarbose is the only new pharmaceutical therapy for non-insulin dependent diabetes that has become available in the last 40 years. See Santeusanio, et al. Drug Safety, 11(6):432-444, (1994), and Bischoff, H., Eur. J. of Clin. Invest., 24, Suppl. 3. 3-10 (1994).
Acarbose acts by competitively inhibiting alpha-glucosidases in the intestinal brush border. Alpha-glucosidases convert nonabsorbable dietary starch and sucrose into absorbable monosaccharides. Inhibitors of alpha-glucosidase delay this conversion, resulting in the slower formation and absorption of monosaccharides. Therefore, these inhibitors reduce the concentration of post-prandial blood glucose, effectively treating hyperglycemia. It has been difficult to find other metabolically active drugs that lack toxicity, as reviewed by Rachman, J., Diabetic Medicine, 12:467-478 (1995). Several synthetic alpha-glucosidase inhibitors have been developed as disclosed in U.S. Pat. Nos. 5,286,877, 5,260,447, 5,157,116, 5,097,023, 5,028,614, 5,004,838, and 4,898,986.
Alpha-glucosidase inhibitors also appear to be useful in the treatment of AIDS. See generally, Ratner, L., and N. Heyden, Mechanism of Action of N-Butyl Deoxynojirimycin in Inhibiting HIV-1 Infection and Activity in Combination with Nucleoside Analogs, AIDS Research and Human Retroviruses, Volume 9, Number 4, (1993); Ratner, L., Glucosidase Inhibitors for Treatment of HIV-1 Infection, AIDS Research and Human Retroviruses, Volume 8, Number 2 (1992); Mohan, P., Anti-Aids Drug Development: Challenges and Strategies, Pharmaceutical Research, Vol. 9, No. 6, (1992). The HIV-1 envelope proteins are heavily glycosylated. Much research has centered on the development of selective inhibitors of oligosaccharide synthesis and processing for use as antiviral drugs.
Alpha-glucosidase is required for proper post-translational processing of the env proteins of HIV. Oligosaccharides on the mature env glycoproteins do not play a direct role in infectivity, but infectivity depends on proper oligosaccharide processing. Without proper processing, the env proteins do not fold correctly, impairing infectivity. Fenouillet, E., et at. J. of Gen. Virol., 72:1919-1926 (1991).
This research has resulted in the development of synthetic alpha-glucosidase inhibitors as disclosed in U.S. Pat. No. 5,286,877, 5,264,356, and 5,097,023. In vitro studies demonstrate these compounds inhibit the infectivity of HIV. U.S. Pat. No. 5,264,356 discloses a method of inhibiting the infectivity of HIV and other retroviruses in vitro by application of alpha-glucosidase inhibitors. One of these inhibitors, N-Butyl deoxynojirimycin, has entered clinical trials. U.S. Pat. Nos. 5,028,614 and 5,089,520 disclose methods of treating human patients infected with retroviruses, including HIV, with alpha-glucosidase inhibitors.